Land vehicles used for excavation work or provided with floor cleaning means are known which are capable of making turns with tight turning radii.
In particular, WO 02/46023 A1 discloses a self-propelled vehicle of the type described above, which has the particular characteristic of having a single driving motor, which can be kinematically connected, by way of functional connection means, selectively to two driving wheels in order to allow to turn the vehicle about the wheel whereto rotation is not transmitted.
These functional connection means are composed, for each driving wheel, by a kinematic connection shaft, which can oscillate, with respect to the structure of the vehicle, about an axis that is parallel and spaced thereto and on which a guiding pulley and a driving pulley are keyed, a first belt connected to a transmission shaft that receives motion from single motor being wound around the guiding pulley and the corresponding driving wheel being connected to the driving pulley by means of a second belt.
In practice, thanks to the oscillation of the kinematic connection shaft, which can be performed by means of appropriately provided control levers, it is possible to vary the tension of the first and second belts and deactivate, if the belts slacken, transmission of motion from the transmission shaft to the corresponding driving wheel. Accordingly, by deactivating the transmission of one driving wheel and keeping the other driving wheel engaged with the single motor, the vehicle is turned about the wheel that is disconnected from the motor and therefore remains idle.
Although this constructive solution is valid from a conceptual standpoint, it has proved to be not fully satisfactory from a practical standpoint, since deactivation of transmission provided by the oscillation of the kinematic connection shaft causes slippage of the belts on the guiding pulley or on the driving pulley, which rather rapidly causes wear of said belts, with a consequent increase in maintenance costs, especially in case of application to cleaning machines, due to the high temperatures reached during their use.